But Grace isn't like other 14-year-olds. At age 10, the otherwise happy, healthy young girl was struck with a rare brain illness.

She was left unable to walk, eat, sit or speak, until she was approved for Sativex - a medicinal cannabis spray.

"I found my voice," she says.

Three tiny bottles get Grace through a month - they help with pain and seizures, and help her speak. They cost $1100, which the family funds through Givealittle donations.

A medicinal cannabis Bill passed its first reading in Parliament on Tuesday, but doesn't go far enough for the Yeats family.

What they really want is to be able to grow their own cannabis. A Member's Bill in the name of Greens MP Chloe Swarbrick would let them do that.

"[It would take] away the stress of where we're going to get the next month's supply from or how we are going to afford it," Tracey explained.

Ms Swarbrick's Bill is being treated as a conscience issue by most parties, so their MPs can make up their own minds, much the same as the same-sex marriage law and euthanasia.

But National will vote against it as a block, only allowing MPs with a strong interest to support it

Grace and mum Tracy will be a human reminder of what MPs are voting on. Because Grace can't get up to the public gallery, they'll sit down in the debating chamber, right beside MPs, as they vote on the issue.